(1) Field of the Invention
The present invention relates to a poly(arylene sulfide) resin composition comprising a mixture of a poly(arylene sulfide) resin and a thermoplastic elastomer, and incorporated therein, a small amount of a crosslinking agent. More particularly, it relates to a poly(arylene sulfide) resin composition comprising a mixture of a poly(arylene sulfide) resin and a styrene/butadiene/styrene block copolymer elastomer, and a small amount of an aromatic polyfunctional maleimide crosslinking agent.
A shaped article having a crosslinked structure, which is obtained from the poly(arylene sulfide) resin composition of the present invention, exhibits a superior impact resistance, elongation and flexibility while retaining well-balanced mechanical properties, thermal properties and shapability characteristic of the poly(arylene sulfide) resin.
(2) Description of the Related Art
Poly(arylene sulfide) resins, especially polyphenylene sulfide (hereinafter referred to "PPS") resins, are practically used as engineering plastics having a superior heat resistance, chemical resistance, rigidity and shapability. Particularly, uses of molding materials reinforced with reinforcers such as glass fibers have recently been expanded mainly in the field of injection molding for the production of electric and electronic parts and the like.
However, an unreinforced PPS resin has a problem in that the resin has a low elongation and is brittle, and therefore, the unreinforced PPS resin is not suitable for use in the field where a high impact resistance and a high flexibility are required, for example, for the production of tubes, pipes and coatings. Moreover, a PPS resin molding material reinforced with a glass fiber or the like has a problem in that the impact resistance is poor because the PPS resin per se is brittle, and therefore, uses of this molding material is currently restricted.
For the purpose of overcoming the defects of the mechanical properties of this unreinforced PPS resin, composition formed by incorporating a rubber or thermoplastic elastomer into the PPS resin have been proposed. For example, Japanese Unexamined Patent Publication No. 56-118456 discloses a composition comprising a PPS resin and incorporated therein, a block copolymer of a vinyl aromatic compound and a conjugated diene compound, and Japanese Unexamined Patent Publication No. 56-115350 and Japanese Unexamined Patent Publication No. 56-115355 disclose a composition comprising a PPS resin and incorporated therein, a modified block copolymer formed by bonding molecule units having a dicarboxylic acid group or its derivative group to the above-mentioned vinyl aromatic compound/conjugated diene compound block copolymer. Moreover, Japanese Unexamined Patent Publication No. 59-113055 discloses a composition formed by incorporating a polyamide, polyester or other thermoplastic elastomer into a PPS resin, and Japanese Unexamined Patent Publication No. 61-148268 discloses a composition formed by incorporating an ethylene/propylene/conjugated diene copolymer rubber into a PPS resin.
Considerable improving effects can be attained in the compositions disclosed in these patent publications, but the impact resistance and flexibility are not improved to desired levels. Furthermore, when the PPS resin is mixed with the above-mentioned rubber or thermoplastic elastomer, the compatibility is not completely satisfactory, and at certain mixing ratios, the appearance of the method article becomes uneven and in some cases, extreme reduction of physical properties occurs.
Japanese Unexamined Patent Publication No. 63-205358 discloses a polyphenylene sulfide composition comprising (a) a polyphenylene sulfide resin, (b) a thermoplastic resin and (c) a maleimide compound. As one example of the thermoplastic resin (b), a maleic anhydride-modified hydrogenated styrene/butadiene/styrene block copolymer is referred to in this reference. When the specified block copolymer and a maleimide compound are incorporated in a polyphenylene sulfide resin, the resultant composition has a low impact strength and elongation as compared with a composition comprised of the polyphenylene sulfide and the specified block copolymer.